Prosthetic liners made of solid elastomer like silicone, copolymer gel, or polyurethane have been commercially available and used for a number of years as the media next to the skin in the majority of lower extremity prostheses.
Such liners have solved many issues like friction and pressure distribution; however, it has been difficult to achieve effective heat and sweat management when using a non-porous interface. For instance, moisture (e.g. sweat or condensation) within the liner can adversely affect limb health. Moisture decreases the friction suspending the liner on the residual limb. This can cause a pistoning action, which describes the relative movement between the liner and the residual limb.
Excessive limb pistoning tends to lead to friction-related injuries such as friction blisters and skin irritation. It also creates the potential for catastrophic failure of the suspension of the limb. Problems such as dermatitis and infection are also common, particularly if the liner and residual limb are not cleaned appropriately or frequently.
Attempts have been made to more effectively remove heat and sweat from liners using different liner type suction interfaces, yet, such interfaces are relatively complex, short lasting, ineffective, uncomfortable, and inevitably prohibit their use with a large majority of users. For instance, one approach includes venting a locking liner by letting air approximately half way up its length and pumping out air distally, with a wicking sock passing the air over the limb. This approach however is rather bulky, complex, and ineffective.
Another approach applies an elevated vacuum to draw sweat across the proximal edge of a prosthetic liner. Sweat however tends to accumulate at the bottom of a liner and elevated vacuum does not reverse that. Further, this elevated vacuum tends to seal in the inside of the liner and the proximal edge, preventing removal of the sweat. In addition, elevated vacuum applied to the proximal edge of the liner tends to cause blisters, making the liner extremely uncomfortable.
Another approach is to cool down the liner, for example, with a tempering buffer in the form of phase change material embedded in the liner body, reducing sweating to a less than desirable degree since the body cannot cool off without perspiration.
There is thus a need for a prosthetic system that provides simple, comfortable, and effective heat and moisture management.